I have a landscaping problem that I have been mulling over for a year now. Maybe someone here can give me some good advice.

At the end of my lawn, I have two very large oak trees and 3 beautiful 15 feet tall beech trees between them. In front of these trees, I have two blue hydrangea that are about 6 feet apart. Right now there are coneflowers and Japanese anemone surrounding the two hydrangea, but it always seems that I needed some evergreen structural plants between the hydrangea and also behind them there to provide more of a structure. Any idea for something that gets 3 hours of morning sun? I thought about rhododendron.